/****************************************************************************
 *
 * Copyright 2016 Samsung Electronics All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied. See the License for the specific
 * language governing permissions and limitations under the License.
 *
 ****************************************************************************/
/****************************************************************************
 * mm/mm_gran/mm_granalloc.c
 *
 *   Copyright (C) 2012 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <tinyara/config.h>

#include <assert.h>

#include <tinyara/mm/gran.h>

#include "mm_gran/mm_gran.h"

#ifdef CONFIG_GRAN

/****************************************************************************
 * Pre-processor Definitions
 ****************************************************************************/

/****************************************************************************
 * Private Functions
 ****************************************************************************/

/****************************************************************************
 * Name: gran_common_alloc
 *
 * Description:
 *   Allocate memory from the granule heap.
 *
 * Input Parameters:
 *   priv - The granule heap state structure.
 *   size - The size of the memory region to allocate.
 *
 * Returned Value:
 *   On success, a non-NULL pointer to the allocated memory is returned.
 *
 ****************************************************************************/

static inline FAR void *gran_common_alloc(FAR struct gran_s *priv, size_t size)
{
	unsigned int ngranules;
	size_t       tmpmask;
	uintptr_t    alloc;
	uint32_t     curr;
	uint32_t     next;
	uint32_t     mask;
	int          granidx;
	int          gatidx;
	int          bitidx;
	int          shift;

	DEBUGASSERT(priv && size <= 32 * (1 << priv->log2gran));

	if (priv && size > 0) {
		/* Get exclusive access to the GAT */

		gran_enter_critical(priv);

		/* How many contiguous granules we we need to find? */

		tmpmask = (1 << priv->log2gran) - 1;
		ngranules = (size + tmpmask) >> priv->log2gran;

		/* Then create mask for that number of granules */

		DEBUGASSERT(ngranules <= 32);
		mask = 0xffffffff >> (32 - ngranules);

		/* Now search the granule allocation table for that number of contiguous */

		alloc = priv->heapstart;

		for (granidx = 0; granidx < priv->ngranules; granidx += 32) {
			/* Get the GAT index associated with the granule table entry */

			gatidx = granidx >> 5;
			curr = priv->gat[gatidx];

			/* Handle the case where there are no free granules in the entry */

			if (curr == 0xffffffff) {
				alloc += (32 << priv->log2gran);
				continue;
			}

			/* Get the next entry from the GAT to support a 64 bit shift */

			if (granidx < priv->ngranules) {
				next = priv->gat[gatidx + 1];
			}

			/* Use all ones when are at the last entry in the GAT (meaning
			 * nothing can be allocated.
			 */

			else {
				next = 0xffffffff;
			}

			/* Search through the allocations in the 'curr' GAT entry
			 * to see if we can satisfy the allocation starting in that
			 * entry.
			 *
			 * This loop continues until either all of the bits have been
			 * examined (bitidx >= 32), or until there are insufficient
			 * granules left to satisfy the allocation.
			 */

			for (bitidx = 0; bitidx < 32 && (granidx + bitidx + ngranules) <= priv->ngranules;) {
				/* Break out if there are no further free bits in 'curr'.
				 * All of the zero bits might have gotten shifted out.
				 */

				if (curr == 0xffffffff) {
					break;
				}

				/* Check for the first zero bit in the lower or upper 16-bits.
				 * From the test above, we know that at least one of the 32-
				 * bits in 'curr' is zero.
				 */

				else if ((curr & 0x0000ffff) == 0x0000ffff) {
					/* Not in the lower 16 bits.  The first free bit must be
					 * in the upper 16 bits.
					 */

					shift = 16;
				}

				/* We know that the first free bit is now within the lower 16
				 * bits of 'curr'.  Is it in the upper or lower byte?
				 */

				else if ((curr & 0x0000ff) == 0x000000ff) {
					/* Not in the lower 8 bits.  The first free bit must be in
					 * the upper 8 bits.
					 */

					shift = 8;
				}

				/* We know that the first free bit is now within the lower 4
				 * bits of 'curr'.  Is it in the upper or lower nibble?
				 */

				else if ((curr & 0x00000f) == 0x0000000f) {
					/* Not in the lower 4 bits.  The first free bit must be in
					 * the upper 4 bits.
					 */

					shift = 4;
				}

				/* We know that the first free bit is now within the lower 4 bits
				 * of 'curr'.  Is it in the upper or lower pair?
				 */

				else if ((curr & 0x000003) == 0x00000003) {
					/* Not in the lower 2 bits.  The first free bit must be in
					 * the upper 2 bits.
					 */

					shift = 2;
				}

				/* We know that the first free bit is now within the lower 4 bits
				 * of 'curr'.  Check if we have the allocation at this bit position.
				 */

				else if ((curr & mask) == 0) {
					/* Yes.. mark these granules allocated */

					gran_mark_allocated(priv, alloc, ngranules);

					/* And return the allocation address */

					gran_leave_critical(priv);
					return (FAR void *)alloc;
				}

				/* The free allocation does not start at this position */

				else {
					shift = 1;
				}

				/* Set up for the next time through the loop.  Perform a 64
				 * bit shift to move to the next gran position andi ncrement
				 * to the next candidate allocation address.
				 */

				alloc  += (shift << priv->log2gran);
				curr    = (curr >> shift) | (next << (32 - shift));
				next  >>= shift;
				bitidx += shift;
			}
		}

		gran_leave_critical(priv);
	}

	return NULL;
}

/****************************************************************************
 * Global Functions
 ****************************************************************************/

/****************************************************************************
 * Name: gran_alloc
 *
 * Description:
 *   Allocate memory from the granule heap.
 *
 *   NOTE: The current implementation also restricts the maximum allocation
 *   size to 32 granules.  That restriction could be eliminated with some
 *   additional coding effort.
 *
 * Input Parameters:
 *   handle - The handle previously returned by gran_initialize
 *   size   - The size of the memory region to allocate.
 *
 * Returned Value:
 *   On success, either a non-NULL pointer to the allocated memory (if
 *   CONFIG_GRAN_SINGLE) or zero  (if !CONFIG_GRAN_SINGLE) is returned.
 *
 ****************************************************************************/

#ifdef CONFIG_GRAN_SINGLE
FAR void *gran_alloc(size_t size)
{
	return gran_common_alloc(g_graninfo, size);
}
#else
FAR void *gran_alloc(GRAN_HANDLE handle, size_t size)
{
	return gran_common_alloc((FAR struct gran_s *)handle, size);
}
#endif

#endif							/* CONFIG_GRAN */
